Fuse peug



Oct. 2, 1951 G. E. HOLMES Re. 23,414

FUSE PLUG Original Filed July 20, 1945 To SuzEw Puua In Soc- 21 INVENTOR.

fieorye E Holmes BY H15 ATTORNEY.

threaded shell;

Reissued Oct. 2, 1951 UNI-TED- S TATE S I PATE OFFICE FUSE PLUG George E. Holmes, Detroit, Mich.

Original No. 2,498,124, dated'Februai-y 21, 1950, Serial No. 606,113, July-'20, 19495.- .kpplication' .for reissue January 20, 1951, :Serial No. 205,941-

" 12 Claims. 101.20.0 1.25)

Matter enclosed in heavy brackets appears in the original patentbuthforms :no part!!! reissue specification; matter printed in italics indicates the additions niade by reissue.-

The present invention relates to fuse plugs of the type which contain aplurality of fuse elements and which permit anew element to be brought into service when the element formerly fin-service is blown.

A fuse plug of this type is shown in my Patent element. The'presentinvention overcomes this inconvenience while-retaining thesimplicity of constructionof the-fuse plug shown in the earlier patent.

Anobject ofthe invention is to provide a'fuse plug of :this :characterin which a new fuse element is brought into service shy/rotation of the A thneaded shell is .a necessary part of anyzfusegplugand by making it rotatable zandmtovidingit with a contact 'member'to engage :the'vanious fuse 1links,rthe same part is :made to serve "a I ouble purpose thereby increasin h eco omy i -m nuf ure.

Other and-fur her obje ts wil ec me appar n .hp nrea ihs the ;;tol o-wins pecification to ether with the accompanying drawing forming a part hereof.

Ref r in to the drawing: Fig l .is asectional view in elevation, Fig. 2 isa sectional plan View along the line Fig-l3 is a sectiona Plan .view taken l n the line 3+3 .Qf F .1. 7

Fig. 4 is a verticalseetion of the head portion, Fig. ,5 is a side .view of the .fuse carrier, I .Fig. .6 i a .s de -vii wsqf he fuse elem nt nit. Fig. 71s -plan view o n r ar ier rin i -7.3 is airagm n ar pla i w of a modifica ion of the vent on and xc p orthe modifica ion is ot wi e the sameas Fi .3.

Referrin to F gl. a h l w head 2 which serves to grip the device when inserting it in a fuse socket or unscrewin it therefrom is shown Provided with a pluralityof longitudinal internal ribs 3 which engage corresponding grpoves ,l'l in fuse carrier. 1. 'The head zand fuse carrier 1 thus rotate together as a unit. Ilead 2 and fuse carrier I are both constructed of suitable dielectric material and head 2 may be of glass permitting oberv as whi f th fus el me ts ha fl h w H ad"? and fus arr er 1 ma be p ssing the .rib 1.6.

gaging ribs '3 or in; any other desired manrier.

An integralIy' formed fuse member comprising a piece of 'fuse metal I4 is shown'with downwardly and radially extending legs l2, each leg constituting an individual fuse element and being necked at-l3 in the usual manner to localize the point of arcing when the fuse element is blown. The width of the necked portion also serves to determine the rating of'the fuse. The fuse elements fit into corresponding upwardlysloping grooves I5 in fuse carrier "1 whichprovide an individual arcing-chamber "for each fuse element. Common contact to the several fuse elements is estab'lished through apin I ll which engages fuse member I4, the pin I (t -being headed at. The lower head at the central bottom projection I'll of fuse carrier 1 is disposed to engage a contact in a fuse'socket in the usual manner.

'I'hreadedcontactshell 6=ls freely rotatably mounted on the assembly-consisting of fuse carrier '1 and head 2. The upper inwardly turned lip 5 of shell 6 engages annular groove 4 in head 2; Thelowe'r portion is provided with an inwardly extending flange Ba which engages the upper surface of base portion'B of fuse'carrier 1 applying suitable contact pressure at the lower head of pin lfl'when the entire assembly'is screwed into a fuse socket. The gap between the lower portion of 'head 2 and the lower-flange" Gaof shell '6 is filled by a partial ring of suitable insulating material adapted to prevent the arc accompanying the blowing of'the' fuse element in service from damaging a fuse element in an adjacent groove. Aninwardly extending spring contact member [8 is permanently connected to the lower internal portion of shell'fi both electrically and mechanically and engages thelower portion of the particular fuse element l2 which is in service. The other elements are insulated by the lower wall of head Zand by barrier ring l9. .Spring 8 is shaped to act in a manner similar to that of a ratchet. Shell 6 maybe rotated in one direction to bring successive fuse elements into service. When moved in this direction it will move outwardly over one of the ribs 1.6 and spring back to engage .the fuse element in the nextogroove. This action serves as a detent mechanism so that engagement with the next fuse element may be determined both by feel and by, the audible click as contact spring 18 snaps back to its normal position after Rotation in the opposite direc ion relative to head 2 and f se carrier 1 .is prevented "by theflcontact spring l8 which'will engagethe sidepf one of theer ove l5- the one turning the fuse.

3 Contact spring l8 may take the form shown in Fig. 3 or it may take the modified form-shown at IS in Fig. 8. It may also take any other desired form embodying the same principle of operation. The switchin action to bring a new fuse element into service may take place either... on rotation to screw the fuse plug into the socket" or on rotation in a direction to unscrew the plug. 1

The shell 6 may be provided with either a right hand Or a left hand thread. The embodiment illustrated shows a right hand thread with a new fuse element being brought into service upon. turning the head in a direction to screw the plug into a fuse socket. The modification required to obtain any other desired combination will be -'obvious to those skilled in the art.

Ordinarily, it will be desirable to have a new fuse element brought into service upon turning head 2 to screw the fuse plug into the socket. This insures that'the fuse plug-mayalways be unscrewed even if it is held by considerable friction. The assembly comprising the glass head portion 3 and the fuse carrying inner core portion in the form illustrated are secured together 6 for common rotation by the interiitting tongue and groove arrangement best shown in Fig. 2. The threaded contact shell 6 however is freely rotatable relatively to this assembly, except for the spring pressed frictional engagement provided by the spring pressed contact pawl 18 in one rotative direction, and in the opposite rotative direction, by the ratchet locking action of the pawl.

For example, Fig. 3 shows the pawl [8 arranged 1 for a contact shell 6 having right hand screw threads, which is standard practice at present at least in the United States. "In this case the turning moments for screwin the device into and out of a fuse socket wi l be applied to the headcore assembly by grasping and turning the annular top flange of the head 2. The spring frictional grip of the pawl l8 with the fuse carrying core, is 1 sufficient to cause the shell to rotate with the head-core assembly for screwing the entire fuse plug into a usual fuse socket until the bottom of the central contact In engages the usual central contact member in the fuse socket, not shown. The screwing of the fuse plug into its socket is permitted in a usual manner since the threaded shell 6,, like all threaded fuses of this general I -class, are made to fit freely in their-fuse sockets.

Once the central fuse plu contact member I0 bottoms in the fuse socket, it-causes a slight frictional jamming action between the threads of the contact shell 6 and the usual threaded wall of the socket sufficient to arrest further rotation of the shell. After this occurs, further rotation of the head-core assembly in a direction to screw the fuse plug into its socket will cause the head-core assemblyto rotate relatively to the thus stationarily held threaded contact shell '6. This relative rotation causes the spring pressed contact pawl I8 to cam over the raised intervening barriers l6 between the grooves for adjacent fuse strips I2. As the spring pressed pawl passes each successive barrier it snaps inwardly into the next succeeding fuse groove in the core 1, contacting the fuse'strip therein.

pawl are audible and also can be clearly felt by When a fresh fuse plug is first inserted in a socket with all of its 1 fuse elements intact, it is immaterial on which .These snappings of the spring pressed contact fuse strip or leg l2 the contact pawl rests. The,

narrow necked blowout portions I3 01 the fuses are visible through the glass of the sides of the head portion 2, and it is thus possible visibly to check the condition of the fuse elements.

When a fuse strip or leg [2 blows, as its destruction by an excess current load is termed,

,the line which the fuse protects should be cleared of the condition which caused the fuse to blow. The head-core assembly then may be rotated in the direction tending to screw the contact shell 6 into its socket, until the first click of the pawl spring is heard and felt by the one doing the turning. When this occurs the next successive fuse strip or leg is contacted by the pawl and the fuse is ready for re-use. When all of the fuse strips Or legs l2 have been blown, the entire fuse plug may be removed from its socket by a. counterrotation or unscrewing of the core-plug assembly.

, As clearly shown in Figs. 3 and 8 this counterrotational or unscrewing torque; moment causes the pawl l8 0;- l8 to lock against theradially disposed wall of the groove in which the pawl is resting. This locking action of the pawl is sufficient to overcome the frictional or slight jamming action which held the threaded shell 6 against rotation during the rotation of the head-core assembly for changing fuse strips l2 as above set forth.

All unblown fuse strips or legsmay be seen through the sides of the glass head 2'. The blowing of one fuse strip or leg I 2 will blacken up its own window section which the glass overlying its enclosing channel aptly may be termed. The blowing action of one fuse strip however is not permitted to spread laterally to other channels or fuse strips, since each channel for a fuse strip. is sealed laterally from adjacent channels by the interfitting of the abutments IS on the plug against the ribbed inner face of the hea as best shown in Fig. 2. The channels for the fuses open into the space between the top of the fuse plug I and the head 2 to permit expansion of the small amount of gas created by the blowing of the fuse. It is obvious from the above description and the accompanying drawings that the interior is not hermetically sealed so that no dangerous pressures can build up in the interior of the glass head 2.

While the fuse carrying plug I may be ad-' hesively secured in inserted position in the glass head 2, it will work satisfactorily if merely inserted therein, so as to have frictional engagement therewith. In such arrangement, even though the plug should be inserted loosely in the head, when the entire fuse plug is screwed into a socket, the contact member In, engaging the bottom of the socket as described previously herein, will force the plug up into properly seated position in the head and squeeze the parts into sealing relation with the insulating washer i9. With the head and fuse carrying plug thus assembled, the fuse carrying plug 1 can be replaced by a new one using the same head for still further economy of operation if desired.

I have shown what I believe to be the best embodiment of my invention. I do not wish, however, to be limited to the embodiment shown but what I desire to secure by Letters Patentis set her secured against relative rotation to the carrier [by engagement with flanges intermediate the grooves] and partially enclosing the carrier, a fuse member having a plurality of [outwardly and downwardly extending] legs each leg forming a fuse element disposed within one of the grooves, a central connection from the fuse member to the lowermost portion of the carrier, a threaded contact shell freely rotatably secured to the head member, [and having an inwardly extending flange portion adapted] said fuse carrier, head member and contact shell being assembled and secured to exert downward pressure on the carrier when the device is tightened into a fuse socket, and a spring contact member carried by the shell and disposed to transmit turning force applied to said head to said shell and to establish successively an electrical connection to each of the fuse elements upon rotation of the shell with respect to the head and carrier.

2. A device as in claim 1 in which a circular member of insulating material is disposed within the shell rotatably therewith intermediate the [lowermost portion of the] head member and the [upper surface of the flange portion of the] shell and is provided with an opening permitting the spring contact member to pass therethrough to establish contact with the fuse elements.

3. A device as in claim 1 in which the contact member carried by the shell successively establishes connection to the fuse elements upon rotation in one direction and prevents rotation of the shell with respect to the carrier in the opposite direction.

4. A device as in claim 1 in which the contact member carried by the shell is secured directly thereto.

5. A device as in claim 1 in which the contact member carried by the shell is secured directly thereto and is further arranged to establish connection successively to the fuse elements upon rotation in one direction and to prevent rotation of the shell with respect to the carrier in the opposite direction.

6. In a device of the class described, a fuse carrier having a plurality of grooves therein arranged around a central rotative axis, a head member having interfitting relation with, and partially enclosing the fuse carrier, and secured to rotate with said fuse carrier, the portions intermediate the grooves comprising barriers, fuse strips in said grooves, a central electrically conductive connection from the fuse strips to the lowermost portion of the fuse carrier, a threaded contact shell freely rotatably secured to said head and fuse carrier, said fuse carrier, head member and contact shell being assembled and secured [a portion of said shell being adapted] to exert downward pressure on the carrier [central connection] when the device is screwed into a fuse socket, and a spring pressed contact member carried by the shell and disposed to transmit turning force applied to said head to said shell and to establish successively an electrical connection to each of the fuse elements on rotation of the head and carrier relatively to the shell.

7. A device as in claim 6 wherein the barriers intermediate the grooves are in sealing contact with the head member.

8. A device as in claim 6 wherein the barriers intermediate the grooves have interfitting relation with correspondingly shaped portions of the head member.

9. A device as in claim 6 wherein the spring contact member comprises an arcuately shaped strip of electrically conductive spring metal shaped to fit conformingly within the contact shell to rotate therewith, and having an inwardly offset pawl end portion disposed to contact successive fuse strips upon rotation of the shell relatively to the fuse carrier in one direction and to prevent rotation of the shell relatively to the fuse carrier in the opposite direction.

10. A device as in claim 6 wherein the spring contact member comprises a pawl having frictional engagement with the secured head and fuse carrier upon rotation of the contact shell in one direction relatively thereto, and having interlocking engagement with said secured head and fuse carrier to prevent relative rotation of the contact shell in the opposite direction.

11. In a device of the class described, a hollow head open at one end and closed at the other, a fuse carrier non-rotatably mounted within said head, a plurality of fuse elements secured to the carrier, a cylindrical threaded contactshell laterally surrounding and rotatable relative to the head at its open end, a contact member carried by the shell and frictionally engaging the carrier to transmit to the shell a turning force applied to the head whereby the device may be screwed into a socket and adapted to successively engage and establish an electrical connection with each of the fuse elements upon rotation of the carrier and head with respect to the shell, and a contact member common to all'of the fuse elements and er:- tending beyond the carrier and the open end of the head to establish contact with a contact element of a fuse socket when the device is tightened therein.

12. A device as in claim 11 in which the contact member carried by the shell successively establishes electrical connection to the fuse elements upon rotation of the carrier and head in one direction and prevents rotation of the shell with respect to the carrier and head upon rotation in the opposite direction.

GEORGE E. HOLMES.

REFERENCES CITED The following references are of record in the file of this patent or the original patent:

UNITED STATES PATENTS Number Name Date 1,437,905 Moss et al. Dec. 5, 1922 1,437,906 Moss et a1 Dec. 5, 1922 1,848,924 Ammerman Mar. 8, 1932 1,914,871 Siampos June 20, 1933 2,058,264 Schiller Oct. 20, 1936 2,206,785 Linton July 2, 1940 2,383,484 Holmes Aug. 28, 1945 

